Gas discharge oscillator



INVENTOR [ZarpwiY/Yma BY ATTORNEY C. W. HANSELL GAS DISCHARGE OSCILLATOR Filed Feb. 28, 1946 i w j W 4/0 \M/lll fl v 57 6M 45 M awrw UMM 9 72 00 2 z WW 0a a a b M5 w 3 0 m w 0 a P 5 MM Q8 x W W? 5 9 1. r w m I. W 0 11 1 w wfl Oct. 5, 1948.

Patented Oct. 5, 1948 2,450,475 GAS DISCHARGE OSCILLATOR Clarence W. Hansell, Port Jefferson, N. Y., assignor to Radio Corporation of America, a corporation of Delaware Application February 28, 1946, Serial No. 650,955

19 Claims.

The present invention relates to the art of producing and controlling alternating current energy and is more particularly applicable to the production of alternating currents having frequencies ranging from 10,000 to 50,000 cycles per second although it should be clearly understood that my invention is not limited to any particular value of frequencies. Such alternating currents have many uses in industry, particularly with regard to induction surface hardening of steel parts, brazing operations, heating of parts in vacuum during manufacture of vacuum devices and induction furnaces for the melting and distillation of various metals and for reducing these metals from their ores.

An object of the present invention is the provision of means for supplying large amounts of alternating power for industrial applications at frequencies ranging from 10,000 to 50,000 kilocycles per second.

Another object of the present invention is the provision of an oscillator which, although a relatively low voltage device, has a high conversion efficiency and is capable of handling large amounts of power.

A further object of the present invention is to improve the operation of gas dischargeoscillator tubes whereby the difficulties previously encountered with such devices, caused by the substantially instantaneous current interruptions in the anode circuit during the oscillating cycle, too often caused break down of associated element circuits.

The foregoing objects and others which may appear from the following detailed description are attained by providing within an evacuated chamber an arc discharge structure including a cathode, an apertured first anode for striking and holding an arc from the cathode and a second anode. The are to the second anod is drawn through the aperture in the first anode. The pumping action of the arc through the aperture causes oscillations to be developed in the second anode circuit. Since the present invention is particularly directed toward push-pull operation of an arc discharge device the first and second anodes are provided in duplicate so that they operate alternately. In the present form of construction, the holes through the first anodes through which the arcs are drawn are so arranged as to face one another. Thereby the current in one orifice results in a blast of ionized gas into the other orifice. The resulting increase in gas density in the other orifice and the injection of ions therein automaticallyresults in its firing to take over the current which is interrupted in the first orifice by the pumping action therethrough. Thus, there is attained an instantaneous transfer of current through one anode to the other in such a manner as to prevent extremely high 'pulse anode potentials at the instant of current interruption at each anode, which would otherwise be caused by inductances in th common power input circuits to the two anodes and the cathode.

The present invention will be more fully understood by reierence to the following detailed description which is accompanied by a drawing in which:

Figure 1 illustrates in section an embodiment of the present invention, and

Figure 2 illustrates a circuit arrangement with which the tube of Figure 1 may be used.

Referring now to Figure 1, there is shown an evacuated casing l0 having on its side walls a pair of opposed mounting flanges or bosses i2 and M. An end of the casing I0 is provided with a mounting flange l5 to which the cathode structure to be described later is attached. An orifice I6 is provided leading into the interior of the evacuated chamber by means of which the chamber may be evacuated to the desired extent and refilled as desired with an ionizable gas. vapor or small amounts of the inert gases such as argon, helium, neon, krypton or xenon may be employed but it also may be possible to use other gases or vapors, such for example, as sodium and potassium. Flanke l5 carries a cathode retaining plate I! to which cathode I8 is connected by means of the cathode supporting stem IS. The cathode I8 is constructed in a generally conventional manner having a filament 20 within its hollow interior by means of which the cathode may be heated.

The exterior surface of the cathode may carry electron emitting fins 2| and the entire surface may be coated with various substances to increase its electron emissivity such as the oxides of barium and strontium. One end of the filament 20 for heating cathode I8 is shown as being directly connected to cathode [8 while the other end is lead out from the casing through a metalglass seal 22. However, it is within the scope of the present invention to utilize an entirely insulated filament if desired by employing a pair of insulated lead-ins through the seal 22 if desired.

The mounting bosses I2 and (one either side of the evacuated casing I0, carry apertured first anodes 24 and 34. They are insulated from cas- Mercury.

ing H3 and an air tight seal is provided by insulating gaskets 29. Back of anodes 24 and 34 are provided second anodes 25 and 35. Anodes 24 and 25 are mounted in position on boss I2 by mounting screws 26 passing through insulating blocks 21 and 2t and into threaded holes in boss 12. Insulating means 27, 2S and 23 serve to electrically isolate anode 24, anode 25 and easing i each from the other. Ancdes 3d .and 35, on the other side of easing l B are simularly held in place and isolated from each other and from casing 10. Anodes 24 and 34 are provided with axially aligned tapered orifices 30 and 40 while second anodes 25 and 35 contain cavities 3i and at aligned with the orifices 38 and '39.

Now, assume that the container H3 is evacuated to a suitable extent, but still contains aellpply of ionizable gas, and that a source of positive potential is applied to anodes 25 and 35 and a somewhat lower source of potential is applied to anodes 24 and en. :If cathode 18 is heated by the appropriate energization of filament 20 an arc or glow discharge will take place to each of the anodes 24 and 34 from cathode i8, similar in character to the discharge through mercury vapor rectifiers and similar'devices. These arcs are continuously maintained during the operation of the device.

A secondary arc will be drawn from the cathode 18 through aperture so in anode 24 to the second anode 25 or through aperture all in anode 34 to anode 35. As the current increases in the secondary arc, say through aperture 36, and the current is made large enough in proportion to the gas pressure, then an unstable pumping efiect takes place therethrough, decreasing the gas pressure within the orifice 30. A blast of ionized gas is thus directed from orifice so into orifice 4B. When the pressure within orifice is decreased to .a certain extent the arc to anode 25 can no longer be maintained. The blast of gases into orifice increases the local gas pressure therewithin to such an extent that an .arc is now set up between cathode is and anode 35. A pumping action similar to that described with reference to orifice 38 now takes place in orifice 4c and eventually the discharge is transferred again to anode 2-5 through orifice 30. Thus, when suitable circuits and power supply are provided for the tube of Figure 1, current can be made ;to flow alternately from anode 25 or anode 35 :to cathode 18, with the result that alternating .current :power can be delivered to a circuit coupled between the two anodes.

A circuit arrangement with which the tube of Figure 1 is adapted to :be operated is shown in Figure '2. The main direct current or alternating current power source 56 may be connected to anodes 25 and 35 through a decouplingchoke 5! andan output transformer primary .52.

The low voltage low-current direct power source 60 is .used to supply positive potentials to first anodes 24 and 34 through a smoothing choke 62 and a variable resistor 6! whereby the current drawn by the arcs to anodes 24 and 34 may be controlled. As is conventional practice cathode i8 is diagrammatically shown as being heated by filament 20 from the commercial alternating current power lines through a step-down transformer 10.

The output transformer carries a secondary winding 53 to which the desired alternating current load such as an induction furnace .or the like may the connected. Condenser 80 may be connected between the two anodes 25 and '35 in 3E! 01. their ;outer surf aces.

order to facilitate the alternate transfer of current from one anode to the other while at the same time preventing excessively high pulse anode potential at the instant of current interruption at each anode.

Arc discharge devices constructed as described above, and of asize not much larger than shown in the drawings, should be capable of providing power outputs ranging up to about '10 to 15 kilo- ,watts with about anode circuit conversion emciency when 600 volts of direct current are supplied by the main power supply source 5%. The are discharge device shown in Figure 1 provides cooling for the anodes by means of the fins Higher cooling efficiency couldbe obtained with more efiicient cooling systems, such as liquid cooling applied through passages bored in the bodies of anodes 25, 35, 2'4, 34.

Most of the losses in the oscillatory system described seem to .occur at the Walls of the orifices 30 and 139. Therefore, efiiciency improves with increasing orifice diameter and with increasing power rating. Thus, as a limit the efficiency may be determined by the power supply voltage and the minimum obtainable arc drop of a gas discharge tube. If mercury is used as a source of ions in :the tube the minimum arc drop would be of the orderof 20 volts. Therefore, the anode circuit conversion efficiency approaches an ultimate value of 98% when a 1,000 Volt power supply is used and would become 99.8% if a 10,000 volts power supply is used.

While I have illustrated a particular embodi- 7 merit of the present invention, it should be clearly understood that it is not limited thereto since many modifications may be made in the several elements employed and in their arrangement to cover any such modifications as fall Within the spirit and scope of the invention.

What is claimed is:

l. A gas dischargedevice including an evacuated casing adapted to contain an ionizable gas,

a thermionic cathode, a pair of first anodeseachhaving an aperture therethrough, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode, means for alternately establishing an arc discharge from said cathode to one of said second anodes.

2. A gas discharge device including an evacuated casing, a thermionic cathode, a pair of first anodes each having an aperture therethrough, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said first cathode, means for alternately establishin an arc discharge from said cathode to one of said second anodes through the aperture in.one of said first anodes.

3. A gas discharge device including an evacuated casing adapted to contain an ionizable gas, a thermioniccathode, a pair of first anodes each having an aperture therethrough, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc d sch rge betw en ach of said first anodes andsaid first cathode, means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in an opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

4. A gas discharge device including a casing adapted to contain an ionizable gas under reduced pressure, a thermionic cathode within said casing, a pair of first anodes each having an aperture there-through and in communication with the interior of said casing, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of first said anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes.

5. A gas discharge device including a casing adapted to contain an ionizable gas'under reduced pressure, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes.

6. A gas discharge device including a casing adapted to contain an ionizable gas under reduced pressure, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, .one in back of the aperture in each of saidfirst anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

'7. A gas discharge device including a casing having apertures in opposite side walls, apertured electrodes insulatingly secured over each of said apertures, anodes insulatingly supported over each of said apertured electrodes, means for maintaining the joints between said casing and said apertured electrodes and between said apertured electrodes and said anodes airtight, a thermionic cathode within said casing and means for maintaining under reduced pressure an ionizable gas within said casing.

8. A gas discharge device including a casing having apertures in' opposite side walls, apertured electrodes insulatingly secured over each of said apertures, anodes insulatingly supported over each of said apertured electrodes, means for maintaining the joints between said casing and said apertured electrodes and between said apertured electrodes and said anodes airtight, a thermionic cathode within said casing and means for maintaining under reduced pressure an ionizable gas within said casing, the apertures in' said electrodes being arranged in coaxial opposition.

9. A gas discharge device including a casing containing an ionizable gas under reduced pressure, a thermionic cathode, a pair of first anodes each having an aperture therethrough, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes.

10. A gas discharge device including a casing, a'thermionic cathode within said casing, a pair of first anodes within said casing and each having an aperture therethrough, a pair of second anodes also within said casing, one in back of the aperture in each or" said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes.

11. A gas discharge device including a casing, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode, means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in an opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

12. A gas discharge device including a casing containing an ionizable gas under low pressure, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough, a pair of second anodes, one in back of the aperture'in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode, means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in an opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

13. A gas discharge device including a casing,

a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathodes and means for alternately establishing an are discharge from said cathode to one of said second anodes through the aperture in one of said first anodes.

14. A gas discharge device including a casing containing an ionizable gas under reduced pressure, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, one in back of the' aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes.

15. A gasdischarge device including a casing, a thermionic cathode within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between 2,460, 4&7 5

each of said first anodes and said'cathodeand means for alternately establishing an are dis-- charge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

16. A gas discharge device including a casing containing an ionizable gas under reduced pressure, a thermionic cathode Within said casing, a pair of first anodes each having an aperture therethrough and in communication with the interior of said casing, a pair of second anodes, one in back of the aperture in each of said first anodes, means for establishing an arc discharge between each of said first anodes and said cathode and means for alternately establishing an arc discharge from said cathode to one of said second anodes through the aperture in one of said first anodes, the apertures in said first anodes being arranged in opposed facing relationship whereby a blast of ionized gas from one of said apertures tends to extinguish an are through the other of said apertures.

17. A gas discharge device including a casing having apertures in opposite side walls, apertured anodes insulatingly secured over each of said apertures, second anodes insulatingly supported over each of said apertured anodes, means for maintaining the joints between said casing and said apertured anodes and between said apertured anodes and said second anodes airtight, a thermionic cathode within said casing and means for maintaining under reduced pressure an ionizable gas Within said casing.

18. A gas discharge device including a. casing having apertures in opposite side walls, apertured anodes insulatingly secured over each of said apertures, second anodes insulatingly supported 5 over each of said apertured anodes, the joints between said casing and said apertured anodes and between said apertured anodes and said second anodes being maintained airtight, a thermionic cathode within said casing, the apertures in said first mentioned anodes being arranged in coaxial opposition, an ionizable gas being maintained under reduced. pressure within said casing.

1.9. A gas discharge device including a conductive casing having apertures in opposite side walls, apertured anodes insulatingly secured over each of saidapertu-res, second anodes insulatingly supported over each of saidapertured anodes, the joints between said casing and said apertured anodes and between said apertured anodes and said second anodes being maintained airtight, a thermionic cathode within. said casing, the apertures in said first mentioned anodes being arranged in coaxial opposition, an ionizable gas being maintained under reduced pressure within 25 said casing.

CLARENCE W. HANSELL.

REFERENCES CITED The following references are of record in the 30 file of this patent:

UNITED STATES PATENTS Number Name Date 2,056,412 Spencer V Oct. 6, 1936 35 2,213,226 Marshall Sept. 3, 1940. 

